attributionControl: value can be {compact: true} to force a compact attribution icon that shows the full attribution on click, or {compact: false} to force the full attribution control. The default is a responsive attribution that collapses when the map is less than 640 pixels wide.

Example:

// map refers to a <div> element with the ID map
// examples.map-4l7djmvo is the ID of a map on Mapbox.com
var map = L.mapbox.map('map', 'examples.map-4l7djmvo');
// map refers to a <div> element with the ID map
// This map will have no layers initially
var map = L.mapbox.map('map');